A liquid crystal panel has a structure with a display side substrate and a liquid crystal driving side substrate facing with each other and a liquid crystal compound sealed therebetween for forming a thin liquid crystal layer. A liquid crystal display apparatus with such a liquid crystal panel assembled carries out the display by selectively changing the amount of the transmission light beam or the reflected light beam of the display side substrate in such manner that the liquid crystal drive side substrate of the liquid crystal panel electrically controls the liquid crystal arrangement in the liquid crystal layer.
For the liquid crystal panel, there are various driving methods such as the static drive method, the simple matrix method and the active matrix method. Recently, as a flat display for a personal computer, a personal digital assistant, or the like, a color liquid crystal display apparatus using a liquid crystal panel of the active matrix method or the simple matrix method has rapidly been spread. Each driving method has several driving modes. For example, in the case of the active matrix method, there are the driving modes such as the TN, the IPS, and the VA. A layered structure of the color filter varies according to the driving mode.
FIG. 1 is a configuration example of a liquid crystal panel of the active matrix method. A liquid crystal panel 101 has a structure produced by having a color filter 1 as the display side substrate and a TFT array substrate 2 as the liquid crystal driving side substrate face with each other so as to provide a gap part 3 of about 1 to 10 μm, filling the inside of the gap part 3 with a liquid crystal L, and sealing the circumference thereof with a sealing material 4. The color filter 1 has a structure with a black matrix layer 6 and a pixel part 7 formed in this order on a transparent substrate 5 from the side close to the transparent substrate, in which the black matrix layer 6 is formed in a predetermined pattern for blocking the light beam in the boundary part between the pixels and a pixel part 7 has a plurality of colors (in general, the three primary colors of red (R), green (G) and blue (B)) arranged in a predetermined order for forming the pixels or recently a pixel part may utilize the hologram. In general, the pixels are formed by applying a photosensitive colored resin composition prepared by dispersing and/or dissolving a color material in a photosensitive resin composition on a substrate and patterning by the photolithography. In this case, the photosensitive colored resin composition may either be of the positive type or the negative type. For the TN mode, a transparent electrode layer 9 is provided on the pixel part 7 or a protection layer 8. For the IPS mode, the protection layer 8 is provided on the pixel part, and the transparent electrode layer 9 may be formed on the side opposite to the pixel part 7 of the transparent substrate 5. Moreover, for the IPS mode, a resin black matrix is essential for the black matrix layer. For the VA mode, a transparent electrode is formed on the pixel part 7 or the protection layer 8 such that the transparent electrode may have a pattern formed. Particularly for the MVA mode, a projected substance called protrusion is formed on the transparent electrode 9.
On the other hand, a TFT array substrate 2 has a structure with TFT elements arranged and a transparent electrode layer provided on a transparent substrate (not shown). Moreover, an orientation layers 10 are provided on the color filter 1 and on the inner surface side of the TFT array substrate 2 facing thereto. In general, a back light is installed as the light source on the outer surface side of the TFT array substrate 2. Then, a color image can be obtained by controlling the light transmittance from the back light by a liquid crystal layer provided on the rear side of the pixels colored in each color. For the back light, a fluorescent pipe called three wavelength pipe or an LED is used mainly. The wavelength distribution of the F10 light source as one of the light sources using a three wavelength pipe is shown in FIG. 7 together with the wavelength distribution of a standard light source C.
As a method for maintaining the cell gap, there are a method of scattering a large number of spherical or bar like particle spacers 11 of a certain size, made of a glass, an alumina, a plastic, or the like as the spacer in the gap part 3, attaching the color filter 1 and the TFT array substrate 2, and injecting a liquid crystal as shown in FIG. 1, and a method of forming a columnar spacer 12 having a height corresponding to the cell gap in the area superimposed with the position with the black matrix layer 6 formed on the inner surface side of the color filter as shown in FIG. 2.
According to the liquid crystal display apparatus with the color filter of the above-mentioned structure assembled, a color image can be obtained by controlling the light transmittance of a liquid crystal layer provided on the rear side of each colored pixel which is arranged in a predetermined pattern.
For the advantage of saving the energy and the space, the liquid crystal display apparatus (LCD) attracts the attention as the display for substituting the conventional CRT monitor, and thus it is currently spread rapidly as a monitor for the OA appliance and the personal computer.
According to the spread of the internet and the portable phone, not only the character information but also the video and the image are distributed so that the images can be traded through the media such as the monitor of the personal computer, the printer, the digital camera and the scanner, and thus the common specification for the color space and the color reproduction compatible to the applications has become necessary. As a representative specification of the image signal transmittance method, there is the sRGB (international standard specification IEC61966-2-1).
It is the chromaticity of the three primary colors (image receiving three primary colors) of the image receiving unit that determines the color reproduction range of the multi media monitor. The three primary colors of the liquid crystal monitor of the sRGB specification are determined as follows as to the chromaticity coordinates x and y in the XYZ color system.
Red: x=0.64; y=0.33
Green: x=0.30; y=0.60
Blue: x=0.15; y=0.06
Moreover, recently, spread of the liquid crystal color televisions is accelerated according to the drop of the liquid crystal panel price. However, in the present situation, it is extremely difficult to provide the liquid crystal color television with the display performance comparable to that of the CRT.
For the color televisions, the shape, the movement and the hue of the object are reproduced on the image screen through the processes of the (1) image pick up (color camera), the (2) transmittance, and the (3) image receiving (image receiving unit), and the transmittance method for the image signal including the hue is standardized. As the representative ones of this method, there are the NTSC (National television system committee) and the EBU (European broadcasting union). The NTSC is adopted as the standard for the television broadcasting method in Japan, the United States, Canada, or the like, and the EBU is adopted in Europe.
It is the chromaticity of the three primary colors (image receiving three primary colors) of the image receiving unit that determines the color reproduction range of the color television, and the spectral characteristics that the color camera should have are also determined thereby. The image receiving three primary colors of the NTSC specification are determined as follows as to the chromaticity coordinates x and y in the XYZ color system.
Red: x=0.67; y=0.33
Green: x=0.21; y=0.71
Blue: x=0.14; y=0.08
On the other hand, the image receiving three primary colors of the EBU specification are determined as follows.
Red: x=0.64; y=0.33
Green: x=0.29; y=0.60
Blue: x=0.15; y=0.06
x=X/(X+Y+Z), y=Y/(X+Y+Z), and x, Y, Z are the three stimulus values in the XYZ color system.
However, in order to realize the excellent display performance of the color television, it is necessary that the color reproduction range satisfies the above-mentioned specification as well as that the screen is bright so that a sufficiently high transmittance is required. In the case of the CRT fluorescent substance, if the color reproduction range is widened too much, the transmittance is lowered extremely. Therefore, in the case of the CRT color television in the present situation, in order to ensure the necessary transmittance, the color reproduction range is sacrificed, and it is restrained to about 75% compared with the displayable space of the NTSC specification.
In order to provide the liquid crystal color television with the display performance comparable to the CRT, it is required that the color reproduction range satisfies the display specification for the color television as well as that the transmittance is sufficient. In order to realize the wide color reproduction range and the high transmittance, the combination of the spectral characteristics of the light source and the color reproduction ability of the color filter is important.
Although the bright line position of the light source spectrum differs depending on the back light manufacturers, the peak is provided at about 545 nm, with the sub bright lines present at the wavelengths before and after the same. Therefore, for the high transmission color filter, a pigment having a high transmittance at 545 nm and the vicinity thereof is required. For the high color purity color filter, a pigment having a narrow half bandwidth with the transmittance provided only at the main bright line is required. Therefore, for the color filters, there are the two kinds of the development element and the demand for the high transmittance and for the wide color reproduction range.
As to the green pixels for the color filter, capability of emitting a strongly yellowish green color is required in order to ensure the high transmittance in the wide color reproduction range. Among the specifications, for the sRGB specification compatible to the multi media monitor, a particularly strongly yellowish green pixel is required. Although a strongly yellowish green pixel is required also for the NTSC, EBU specifications compatible to the television, a bluish green setting is provided compared with the sRGB specification. However, in the case of adopting any display specification, it is extremely difficult to form a green pixel close to the green color of the three primary colors capable of ensuring a sufficient color reproduction range with a high brightness by only one kind of a green pigment. Then, in order to ensure a sufficient transmittance in a sufficient color reproduction range, it is desired to form a pixel having a high transparency with a high color strength while restraining the total use amount of the pigment by sufficiently developing the color in such manner that a green pigment having a high transmittance in the vicinity of 545 nm, which is the green wavelength while restraining the transmittance of the sub bright line is mainly used in combination with a yellow pigment having a high transparency.
As conventional green pigments for the green pixel of the color filter, C. I. pigment green 7 (hereinafter PG7) made of a chlorinated copper phthalocyanine pigment, and C. I. pigment green 36 made of a brominated copper phthalocyanine pigment (hereinafter PG36) have been used mainly. Although the PG7 has a strong green color strength, it has too strong a bluish tinge, a large amount of yellow needs to be mixed for having a green color for the pixels of the sRGB, NTSC and EBU specifications. Furthermore, since it has a low transmittance, a dark color filter is provided in the case the green pixels are formed mainly with the PG7. On the other hand, since the PG36 shows a relatively yellowish spectral transmittance spectrum and a wide half bandwidth with a wide spectral transmittance width in the vicinity of the peak top so as to transmit the bright line in the sub wavelength range, it shows an extremely high transmittance, however, it has a low color strength. Therefore, in order to form the green pixels for displaying a range with a high color strength (high density region) on the color coordinates, the PG36 pigment use amount is large so that the pixel transmittance becomes low. Even though there is a method of offsetting the color coordinates to the yellow direction by raising a concentration of the yellow pigment in order to ensure the high transmittance, such method requires large mount of the yellow pigment, thus total use amount of the pigment becomes larger. Therefore, a pigment capable of taking place of the conventional halogenated copper phthalocyanine pigments such as the PG7 and PG36 has been called for.
In general, in the case the composition ratio of pigment in the photosensitive color composition (photosensitive colored resist) is increased, the transparency of pixel is lowered so that the transmittance can hardly be raised. Moreover, in the case the composition ratio of pigment in the color filter forming photosensitive color composition is increased, the composition ratio of dispersing agent is increased as well so that the composition ratio of the components related to the film forming property such as the binder or the developing component becomes relatively small. In the case amount of the binder or the developing component is small, a problem is involved in that an adverse effect is posed to the minute pattern forming ability and the physical property of the pixels. Moreover, in the case of using a pigment having a low color strength, if the composition ratio of pigment in the photosensitive color composition is restrained, the film thickness needs to be made large for coloring. Also in the case of having a film thickness large, a problem is involved in that an adverse effect is posed to the minute pattern forming ability and the physical property of the pixels.
For example, in the case of producing a pixel minute pattern by the so-called pigment dispersing method, as to the minute pattern forming ability, performances such as no residue, no remaining foreign substances, a high resolution, an accurate shape after development and an even film thickness are required.
The residue is colored substances remaining at a portion whereat they should not remain after development. It may easily be generated in the case of a poor developing property for the reasons such as a large amount of the pigment or the dispersing agent. The foreign substance can be generated for the causes such as a partial lacking of the pixels in the case the curing component in the photosensitive color composition is little, and adhesion of the colored piece generated by the peeling phenomenon due to little developing component. In order to improve the resolution, patterns with many curved portions or corners unlike the conventional stripe patterns have appeared also for the color filter owing to the advancement of the liquid crystal driving method. Also for such a complicated pattern, accurate formation is required.
A problem is involved in that the shape after the development becomes an inverse trapezoid (inverse tapered shape) in the case the photosensitivity of the photosensitive color composition is poor. In the case the shape after the development is inverse trapezoidal, due to the tendency of lacking the pixel upper part by the hydraulic pressure at the time of the development, or the like, it provides the cause for the above-mentioned foreign substance generation. Furthermore, in the case of an inverse trapezoidal layer having a low heat resistance, a void may be formed after post baking due to sagging of a portion protruding like a hood by the heat. The void not only deteriorates the display quality but also lowers the resolution. Moreover, if the void portion bursts by the heat at the time of assembling the liquid crystal panel, the liquid crystal is polluted.
The evenness of film thickness does not cause a major problem at the individual pixel level. However, the substrate size keeps on enlarging for the purpose of the cost reduction, thus a meter class comes to be adopted. In that case, if the film thickness differs at the glass center and the end parts, the color becomes irregular so as to provide a defective product.
Moreover, as to the physical properties of the produced pixels, performances such as the hardness, the elasticity, and the impurity eluting property are required.
In order to form a high color purity liquid crystal display apparatus, it is preferable to provide a columnar spacer selectively in an opening area without using a spherical spacer, which deteriorates the display quality. However, even if a high hardness columnar spacer is formed, if the hardness or the elastic modulus of the pixel or the black matrix is poor, the cell gap evenness is deteriorated due to the deformation of foundation.
Therefore, even for the pixels, the high hardness and elastic modulus are required. However, if the composition ratio of the pigment or the dispersing agent in the photosensitive color composition is made larger and the binder amount is made smaller thereby, it is impossible to provide the sufficient hardness or elastic modulus to the pixels.
The impurity elution from the pixels causes the liquid crystal pollution. Since the liquid crystal does not perform the switching function only by the introduction of a small amount of the conductive impurities, it is important that the conductive molecules do not elute from the color filter to the liquid crystal layer. However, the conductive molecules are included as the impurities in the pigment or the dispersing agent used for the pixels. Therefore, it is important to restrain the impurity elution by scavenging the molecules with a dense mesh by raising the cross linking density of the layer.
On the other hand, Japanese Patent Application Laid-Open (JP-A) No. 2002-131521 discloses a composition for a color filter containing at least one kind of a phthalocyanine based pigment having as the central metal VO, Al-Z or In-Z (Z represents a halogen atom, a hydroxyl group, an alkoxy group or an aryloxy group). Moreover, JP-A No. 2002-162515 discloses a composition for a color filter containing as a color material C. I. pigment green 7 and/or C. I. pigment green 36, wherein the composition further contains a phthalocyanine based pigment having a maximum transmittance wavelength longer than that of the C. I. pigment green 7 and C. I. pigment green 36. However, the above-mentioned phthalocyanine pigment is used by mixing with the C. I. pigment green 7 and/or C. I. pigment green 36.
Moreover, as those disclosed after the earliest priority date of the present invention, there are the following three patent documents. JP-A No. 2002-250812 discloses a color composition for a color filter containing a green coloring material made of a halogenated copper phthalocyanine pigment and at least one kind of a halogenated different kind metal phthalocyanine pigment with the central metal selected from the group consisting of Mg, Al, Si, Ti, V, Mn, Fe, Co, Ni, Zn, Ge and Sn, with a 1 to 80 mole % content amount of the halogenated different kind metal phthalocyanine pigment based on the total amount of the green coloring material. The above-mentioned halogenated different kind metal phthalocyanine pigment is used as a mixture with the halogenated copper phthalocyanine.
JP-A No. 2003-161821 discloses a composition for a color filter containing a pigment, wherein the composition further contains one kind or two or more kinds of the phthalocyanine based compound selected from the group consisting of a phthalocyanine based compound having no central metal and a phthalocyanine based compound having a central metal other than the copper. It discloses that the above-mentioned phthalocyanine based compound is used by a relatively small amount.
JP-A No. 2003-161827 discloses a color filter characterized in that (1) a green pixel part contains a halogenated metal phthalocyanine pigment with 8 to 16 halogen atoms per one phthalocyanine molecule bonded with a benzene ring of the phthalocyanine molecule and (2) the green pixel part shows the maximum transmittance at 520 to 590 nm in the spectral transmittance spectrum in the whole range of visible light beam.
However, a green pigment having the excellent color strength and the high transmittance and a photosensitive color composition, which are capable of satisfying the purpose of forming a color filter having a wide color reproduction range and a high transmittance have not been known yet.
The present invention has been achieved in view of the circumstances, and a first object thereof is to provide a green pigment for a color filter, capable of displaying the chromaticity coordinates not to be displayed by the conventional green pigments, having the excellent color strength as a green color without too strong in a blue tinge, and a high transmittance.
Moreover, a second object of the present invention is to provide a photosensitive color composition using the above-mentioned green pigment, which is capable of forming a color filter having a wide color reproduction range and a high transmittance.
Moreover, a third object of the present invention is to provide a photosensitive color composition using the above-mentioned pigment, which is capable of getting closer to the green pixel of each specification with a relatively small amount of the pigment, thus having a high composition ratio of the reactive component and the excellent make-up property in printing.
Moreover, a fourth object of the present invention is to provide a photosensitive color composition using the above-mentioned green pigment, which is capable of forming a green pixel having a green color developing property with a sufficiently strong yellowish tinge even with a small mixing amount of a yellow pigment.
Moreover, a fifth object of the present invention is to provide a photosensitive color composition using the above-mentioned green pigment in combination with the other specific green pigment, which is capable of achieving the above-mentioned second to fourth objects by a thinner film thickness.
Moreover, a sixth object of the present invention is to provide a pigment dispersion using the above-mentioned green pigment, which is suitable for preparing the above-mentioned photosensitive color composition.
Moreover, a seventh object of the present invention is to provide a color filter with the green pixel formed using the above-mentioned photosensitive color composition, and a liquid crystal panel using the color filter, which have a wide color reproduction range and a high transmittance.